The present invention relates generally to electrical switching devices and methods, and more specifically to a circuit breaker apparatus which dynamically sets its current trip level based on information communicated from the load.
Many situations exist in which power circuit faults may be dangerous or even catastrophic, ranging from the risk of electrical bums or electrocution in the home, to the triggering of fires or explosions in industrial settings. Aircraft, including a commercial airliner, have been lost as a result of frayed insulation on wires running through fuel tanks; spacecraft have been severely damaged by wiring faults, and explosions in mines and factories have been caused by electrical short circuits.
Existing circuit protection devices, such as fuses, circuit breakers, and ground fault interruptors (GFI) are important safety components, but are limited in the types of electrical faults they protect against.
Circuit breakers and fuses are typically xe2x80x9csizedxe2x80x9d to limit the current in a circuit to the maximum current that may be safely carried by the power distribution circuit wiring. Thus, a circuit breaker may be sized at 20 to 100 Amperes based on the current carrying capacity of the power distribution wiring, even though the appliance or electrical machinery the circuit breaker feeds may require only a few amperes of operating current. A dangerous electrical fault may thus exist, drawing many amps of current, without tripping a circuit breaker or blowing a fuse.
Ground Fault Interruptor (GFI) protective circuits are also well known in art. GFI circuits interrupt the application of electric power to a load in response to an imbalance of a predetermined magnitude in the current flowing through the current-carrying wires connected between the source and the load. Typically, a ground fault interrupter circuit uses one or more differential transformers to monitor the current through the xe2x80x9chotxe2x80x9d and xe2x80x9cneutralxe2x80x9d lines extending between a load and a source of power and generates a fault signal whenever the imbalance between the currents in the hot and neutral lines exceeds a predetermined value. When the two currents differ, indicating that some portion of the line (or xe2x80x9chotxe2x80x9d) current has found an alternative path to ground, the GFI trips and shuts off the circuit.
Initially installed in public and commercial settings where electrical equipment was used around water, GFI circuits are now used universally in new construction wherever a likelihood of electrical equipment coming into contact with water exists, such as in bathrooms and kitchens. GFI circuits afford an important degree of protection against electrocution hazards where an individual may inadvertently come into contact with a xe2x80x9chotxe2x80x9d electrical source while another portion of the individual""s body is grounded.
GFI circuits, however, do not adequately protect against situations involving xe2x80x9clinexe2x80x9d (or xe2x80x9chotxe2x80x9d) to neutral faults. In such faults, the currents in both the hot and neutral lines will increase equally with the fault current flowing along the hot line, through the fault, and returning along the neutral line. To a GFI circuit, the fault would appear as simply an increase in the electrical load current. If the fault current did not result in the total load current exceeding the trip level of the circuit breaker of the power distribution system, no protection against the fault would be provided.
There is thus a need for circuit protection devices and methods which provide an increased level of protection, particularly in situations where a relatively minor electrical fault may have catastrophic consequences.
It is an object of the present invention to provide a xe2x80x9csmartxe2x80x9d power circuit protection device which dynamically sets its trip level based upon information received from the load, or power consuming, device.
It is a further object of the invention to provide xe2x80x9csmartxe2x80x9d circuitry for power consuming devices, such that the power consuming devices may report their power requirements to the smart power circuit protection device.
It is a still further object of the invention to provide a smart power circuit protection device which dynamically sets its trip level based upon information received from a plurality of loads by summing the load requirements of the different loads.
It is a still further object of the invention to provide an adapter device allowing power consuming devices which lack a xe2x80x9csmartxe2x80x9d power requirement reporting capability to be used with the smart power circuit protection device.
The present invention also provides methods of setting a trip level in a power circuit protection device based upon information received from the electrical load; methods of reporting power usage requirements from an electrical load to a power protection device; and methods of using electrical devices lacking a power usage reporting capability with a smart power protection device.